It has been found advantageous to rotate the valves of an internal-combustion engine each time same are opened and/or closed for a wiping action that has been found to keep the valves clean and to greatly increase the valve service life. Such rotators are described in U.S. Pat. Nos. 1,520,272 and 1,610,409.
German published patent application 2,841,489 describes a valve rotator using a pair of coil springs that are nested within each other and that are of opposite hand. Each such spring is connected via a respective oppositely effective one-way clutch to one of two spring plates between which it is braced, so that as the valve stem connected to one of these plates moves up and down it is rotated in angular increments by the springs, with a short rotation with each upward movement and a short rotation in the same direction with each downward movement. The disadvantage of this system is that the valve rotation rate is directly related to engine speed. Furthermore the rotation is dependent on many factors, such as friction in the valve guide, inertia, and the like that have different effects at different speeds.
Further rotators are known from German patent documents 1,955,820, 2,110,708, 2,116,086, 2,640,383, and 2,757,455 which all have roller or slide bodies that concentrically surround a base provided with pockets having angled flanks. Springs arranged at an angle to the displacement direction of these bodies bear on these flanks so that as the valve opens they are loaded, and when the valve closes the force stored in them turns the valve an increment. Such an arrangement aims at uniform rotary displacement of the valve. The mechanism is, however, so very complex that this arrangement normally has a short service life, it being noted that such a valve rotator is subject literally to millions of actuations during its normal service life.
Other complicated structures that are connected to the upper spring plate of the valve spring are described in German patent documents 2,054,349, 2,054,351, 2,054,362, 2,128,110, and 2,739,403. Installation of these arrangements in existing engines is virtually impossible. In addition they are normally so bulky that they cannot be employed in engines intended to operate at high RPM due to their large inertia.